Fergus Lyon, a professor and researcher at Middlesex University, makes an important point as funders and nonprofits focus increasingly on metrics: don't forget to evaluate your evaluations. Measuring impact is important, Professor Fergus writes, but unless the methods for generating data are constant, comparing the numbers can be downright misleading.

In particular, Lyon cites impact and effective ratios—"for every pound invested, there is a social value of five pounds"—as an often-used but poor comparison between organizations. Caveat funder.